Critical behavior in a non-asymptotically free version of the SU(3)c×SU(2)L×U(1)Y model

The non-perturbative unification of the SU(3)c⊗SU(2)L⊗U(1)Y model, a la Maiani, Parisi and Petronzio is described in terms of critical exponents at a common Landau singularity. The exponents are evaluated using renormalization group techniques. Numerical integrations of the renormalization group equations are performed, including three-loop diagonal effects. The currently accepted values of the gauge couplings αi(MW) at the weak boson mass scale are reproduced only when there are precisely eight generations of fermions with masses not bigger than the weak boson ones. A large number of Higgs doublets is favoured (NH=7±3). The unification scale is found to be around 1015 GeV.